1. Field of the Invention
The present invention relates to novel olefin oxidation catalysts. Work leading to the present invention was conducted under National Science Foundation Grant No. 86 18766.
2. Prior Art
It is known to oxidize olefins with oxygen to produce oxygenated derivatives at the olefinic double bond, e.g., epoxides, or to cleave the olefinic double bond to yield aldehydes, alcohols, etc. It is also known to oxidize cyclic alkanes with O.sub.2 to produce alcohols and ketones.
It has been attempted to optimize these methods by carrying out the oxidations in the presence of catalysts. Ethylene has been converted to ethylene oxide over a supported silver oxide catalyst [Kitty et al, Cat. Rev., Vol. 10, p. 1 (1974)]. Catalyzed norbornene oxidations are described by Taylor et al, J.A.C.S., Vol. 109, p. 2770 (1987); Taylor et al, J.A.C.S., Vol. 108, p. 2782 (1986); olefin epoxidations, Bailey et al, Chem. Comm., 179 (1987), Balavoine et al, Tett. Letters, Vol. 25, p. 3187 (1984) and Meunier, Bull. Chem. Soc. France, 578 (1986). Cyclohexane is presently commercially oxidized to adipic acid using cobalt (II) napthenoate as a catalyst. [Berezin et al, "The Oxidation of Cyclohexane", Pergamon Press: Oxford, 1966)]. Common catalysts for such oxidations include silver/silver oxide, cobalt (II) napthenoate, vanadates, molybdates etc.
The disadvantages inherent in these known oxidation methods are that they require relatively high temperatures and pressures and the reaction media are highly corrosive.
Although previous studies of the fundamental chemistry of trinuclear ruthenium carboxylate complexes have appeared in the literature [Cotton et al, J. Chem. Soc. Chem. Comm., 967 (1971); Spencer et al, J. Chem. Soc., Dalton Trans., 1570 (1972); ibid, 786 (1974); Cotton et al, Inorg. Chem. Acta., Vol. 6, p. 411 (1972); Wilson et al, J. Am. Chem. Soc., Vol. 97, p. 2285 (1975); Baumann et al, Inorg. Chem., Vol. 17, p. 3342 (1978); Baumann et al, Inorg. Chem., Vol. 18, p. 2472 (1979) and Walsh et al, Inorg. Chem., Vol. 18, p. 2472 (1979)], it is only in the past few years that these compounds have been utilized as catalysts [Legzdins et al, J. Chem. Soc., Dalton Trans., 3322 (1970); Mitchell et al, J. Chem. Soc., Dalton Trans., 846 (1973); Sasson et al, Tetrahedron Lett., Vol. 47, p. 4133 (1974); Sasson et al, Can. J. Chem., Vol. 52, p. 3825 (1974); Fouda et al, Inorg. Chem., Vol. 17, p. 3213 (1978); Milner et al, J. Organomet. Chem., Vol. 152, p. 193 (1979); Fouda et al, Inorg. Chem., Vol. 18, p. 1 (1979); Sasson et al, J. Mol. Catal., Vol. 6, p. 289 (1979); Trzeciak et al, J. Oxid. Comm., Vol. 1, p. 295 (1980); Trzeciak et al, J. Mol. Catal., Vol. 10, p. 69 (1981); Carlsen et al, J. Org. Chem., Vol. 46, p. 3936 (1981); Shibaeva et al, Vestsi Akad. Navuk BSSR, Ser. Khim. Navuk, 40 (1982); Thivolle-Cazat et al, J. Chem. Soc., Chem. Commun., 1128 (1982); Ito et al, Tetrahedron Lett., Vol. 24, p. 5249 (1983); Nicolaides et al, J. Mol. Catal., Vol. 24, p. 375 (1984) and Trzeciak et al, J. Mol. Catal., Vol. 39, p. 85 (1987). A recent report [Bilgrien et al, J. Amer. Chem. Soc., Vol. 109, p. 3786 (1987)] that Ru.sub.3 O(O.sub.2 CR).sub.6 L.sub.3.sup.n (R=CH.sub.3, C.sub.2 H.sub.5 ; L=H.sub.2 O, PPh.sub.3 ; n=O, +1) is an efficient catalyst for the selective oxidation of primary and secondary alcohols to aldehydes and ketones using molecular oxygen as the oxidant is the only reported instance of O.sub.2 activation by these trimers. This result encouraged attempts to use this complex as a catalyst for other substrates; however, attempts to oxidize olefins were unsuccessful. Rhodium carboxylate dimers showed intriguing differences in acidity [Drago et al, Inorg. Chem., Vol. 21, p. 2196 (1982) when carboxylate ligands were exchanged for fluorinated carboxylates, including the reported [Doyle et al, Inorg. Chem., Vol. 23, p. 3684 (1984) ability of the trifluoroacetate dimer to bind olefins. Previous attempts to prepare ruthenium trifluoroacetate trimer were unsuccessful [ Spencer et al, supra].
It is an object of the present invention to provide novel complexes useful as olefin oxidation catalysts, a method for their preparation and an improved olefin or alkane oxidation method utilizing the complexes of the invention.